Some time ago, I promised that I would tell the story of my transition from experimental particle physics to theoretical optics.  With a lot of busy stuff going on at work and my research blogging efforts mired in some rather difficult reading, this seemed like a good time to share the story!

Before I begin, though, let me make a disclaimer: none of this should be interpreted as bashing on particle physics!  I have a soft spot in my heart for the field, and the research is getting very exciting with the gradual startup of the LHC.  This is really a story of how I chose my particular field of research, and how that decision involved balancing the nature of the research with the actual day-to-day work involved.  Most of my choices and rationalizations at the time were from the perspective of an unknowingly clinically depressed graduate student who hadn’t quite figured out what he wanted to do with his life.

One curious thing about my life are my cyclic bursts of energy and motivation.  Every few years, it seems that I subconsciously get bored with some aspect of my life and suddenly undertake a variety of ambitious and extended projects.  The most recent of these, I think, involved my stopping at a music store one day after work on a whim and signing up to take guitar lessons.  The first I recall was near the end of my undergraduate years.

I did my undergraduate work as a physics major at the University of Chicago.  For a large portion of my life, I’ve been a rather passive individual, “going with the flow” without making big efforts to achieve my own dreams.  For example, in my junior year, I remember meeting one of my first-year professors on the quad.

“Still a physics major?” he asked.

“Yeah, I can’t think of anything better to do,” I replied, which sort of ended the conversation.

My statement was bitter, but rather honest; somewhere in the back of my mind I was convinced that I was carrying on a physics degree until I found my true calling, whatever it was.  Nearing the end of that junior year, though, I realized that I needed to get more involved if I was even to continue in physics in grad school.

I exploded into action: I got myself a summer job in an experimental particle physics research group, and made plans to do an (optional) senior physics thesis which would graduate me with honors.  I decided to become a physics tutor, and I took up two martial arts, karate and aikido, on the side. I agreed to be a student marshal, which meant that I would help out at graduation, and I even volunteered to be a resident assistant in my dorm.  (Sometime around then I also started working at GenCon gaming convention, which went on for seven years, but that’s another story.)

I had a good time doing my thesis.  I ended up constructing and testing, from someone else’s design, an analog electronic circuit which could measure the energy output of a particle calorimeter.  The analog design was discarded in favor of the digital version, but I still learned a lot.  I had a great post-doc directly advising me, who I can credit with breaking me of a lot of bad habits (such as saying “I understand” when I didn’t understand), and was indirectly supervised by the head of the project, one of those people who is very nice but, by virtue of his intelligence and authority, scared the hell out of everyone.  (He once walked by the lab, poked his head in to say, “Hi!” and I nearly hit the ceiling.)

After graduation, I stayed on in the lab for another year and then applied to graduate school, and got accepted to the University of Rochester.  I did a TA for a year and then settled into working with an advisor doing experimental particle physics.

Things kind of drifted along aimlessly then for a while, and I gradually started to lose my enthusiasm over particle physics.  Part of this was the environment: I went from a school very strong in particle physics (Chicago) to a school very strong in optics, and the enthusiasm level just didn’t seem as high for the particle stuff.  Part of this was due to the recent demise of the SSC (superconducting super collider), which was supposed to fill the role that CERN’s new Large Hadron Collider now holds: discovering new physics through unprecedented high-energy collisions.  I actually was a “fly on the wall” during one of the strategy discussions when the UofC physicists were deciding how to convince Congress to save the accelerator.  Around the time I started graduate school, particle physics felt a bit like it had the wind knocked out of it.

Lots of little things started to drive me nuts, though it is important to keep in mind that I was suffering from clinical depression and very little would have made me happy back then.

I spent one day in the accelerator tunnels assisting an engineer during his inspection of the accelerator beamline.  When he found an area which wasn’t quite level, he would use a crowbar to force a pipe high enough to stuff a shim underneath it — not exactly what I was expecting!  At one point during the inspection, he had to give a quick ten-minute tour of the lab to visitors, and told me to wait in the tunnel.

There were no chairs down there, so I started looking for somewhere along the wall where I could prop myself and wait.  But everywhere along the beamline, there were these little chalkboards, marked with the dosage of radiation I would get by standing in their vicinity.  I walked probably half of the tunnel looking for a non-radioactive part of the tunnel, to no avail!  To be fair, the radiation level was essentially negligible for the amount of time I was spending there, but it did make me wonder whether I liked the work enough to get any extra radiation exposure.

Part of the difficulty of getting involved in particle physics is the rather steep learning curve: the physics is very non-intuitive and the techniques are elaborate.  Searching for new physics requires first learning to interact with a massive catalog of simulated collision events.  By working with this data set, one can develop a set of “cuts” which will in principle eliminate all the false positives and only leave those events which represent the new physics.  Even then, one needs a very good understanding of statistics to interpret whether or not the detected results are statistically relevant or not.

One day, after having worked for months on developing a great set of cuts to search for “rare-B” decays (rare, non-standard model decays of the bottom quark that would represent new physics), I proudly showed off my proposed cuts to one of the post-docs working on the project.  His response, in effect, was: “Don’t put too much faith in that simulation catalog.  We know it’s not very accurate.”  WTF?  Then what was I doing working with it for all that time???

Particle physics experiments are massive undertakings that require a large group working in collaboration to build and maintain both the detector and accelerator.  One necessary side effect of this is that research results end up being published with the entire group as co-authors, and the groups can be ridiculously large: the CDF collaboration, which discovered the top quark at Fermilab, had at the time some 300 members.  To my mind, I was just as troubled by the possibility of other people co-authoring (and taking credit for) my work as I was by the possibility of my name being associated with work I had no direct role in.

The final straw for me, though, was:

THE TUBE!!!!!

I, or more accurately, my advisor, was assigned the task of testing a prototype for the inner tube of the new detector’s drift chamber.  A particle detector is built around the “tunnel” the particles travel through.  The particles collide head-on in the center of this detector, and charged particles produced in the collision scatter out through the drift chamber, a large collection of densely packed, highly-charged wires (via NobelPrize.org):

The charged particles are detected by the wires, and a powerful magnet curves the trajectories of the particles, allowing a measurement of their momentum.  A sample event measured by the CDF detector is shown below (via DOE Pulse):

The wire chamber is in a vacuum — the wires would discharge in air — so the 12-inch diameter inner cylindrical wall of the chamber must be airtight.  It must also be temperature resistant (the wires get hot), and must be precisely round to within around a 100 micron tolerance, which is the distance of the closest wires to the wall.  We received a prototype carbon fiber tube, and it became my job to test the damn thing.

For. A. Whole. Year.  It took FOREVER to do the measurements.  It is very difficult to set up and operate a system to measure the roundness of a 1-meter long, 12-inch diameter tube to micron precision — and wasn’t even close to round.  It also leaked air profusely.  The final straw, after a year of measurement, was to put a small slice of it into an oven at 100 degrees and see what happened.  The thing came out a hugely distorted ellipse!  The tube, like my undergraduate circuit project, ended up not being used.

At that time, I started reflecting on my career.  I had just spent most of the year measuring a TUBE!  I couldn’t imagine how that would look on my future resume.  I was frustrated, and didn’t think my career was going anywhere.

It was then that I had another one of my bursts of ambition.  Like many young physicists, I had gotten into science with the dream of becoming a theoretical physicist.  Why, then, had I ended up in experimental work?  Partly it was due to inertia — I was following the path that started with my undergraduate particle physics job.  Partly, though, I realized that going into a large experimental physics group was my way of “playing it safe” and finding a career where I felt I could “hide” amongst a crowd.

I emphasize again that this isn’t the way particle physics works — rather, it was my rather immature and inaccurate view of the way it works.  Nevertheless, I realized that I really wanted to do theoretical work, and wondered how to make it happen.

I was lamenting my state to a classmate in Taco Bell a short time later and he suggested that I could possibly work for his advisor, a distinguished theoretician.  I joined the research group and started life as a theoretical optics researcher.  My work was no longer the “fundamental” physics I had originally aspired to, but I found that I loved it nevertheless.

This wasn’t the end of my troubles, of course; theoretical work has its own downsides.  A few years later, with my grad work floundering, I had another burst of energy and took up skating, skydiving, long-distance running and kung fu.  A few years after that, I got treated for my depression, and a final burst of energy got me graduated and on my way to Amsterdam to postdoc.

If there is some bigger point to this post, I guess I should direct it to aspiring scientists.  When choosing a field of research, you should consider whether not only the topic of study but also the methodology is something you enjoy.  Also, make sure you choose a research field because it is truly what you want to do, and not simply what you are doing to “play it safe.”